ALSA: hda: uninitialized variable fix

Commit eaa9b3a748539651f50e3a234c8854e1b42a839a introduced the following
uninitialized warning:

	sound/pci/hda/patch_realtek.c: In function 'set_capture_mixer':
	sound/pci/hda/patch_realtek.c:4928: warning: 'pin' is used uninitialized in this function
	sound/pci/hda/patch_realtek.c:4918: note: 'pin' was declared here

It appears indeed that 'pin' needs to be initialized to 0.

Signed-off-by: Frederik Deweerdt <frederik.deweerdt@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/patch_realtek.c

@@ -4915,7 +4915,7 @@ static void fixup_automic_adc(struct hda_codec *codec)
 static void fixup_single_adc(struct hda_codec *codec)
 {
 	struct alc_spec *spec = codec->spec;
-	hda_nid_t pin;
+	hda_nid_t pin = 0;
 	int i;
 
 	/* search for the input pin; there must be only one */